1. Field of the Invention
The invention relates to an effluent purifying system that enables the reuse of the circulating effluent upon purification. More particularly, the invention relates to a purification method and apparatus for cleansing water of a water bath in a chiller unit used in poultry processing so the chiller wastewater can be recycled and subsequently recirculated throughout the chiller.
2. Description of Related Art
Water traditionally has been a key processing medium in food processing plants. Water is used throughout all steps of the food production process, including food cleaning, sanitizing, peeling, cooking and cooling. Water also is used as a conveyor medium that transports food materials throughout the process. Water additionally is used to clean the equipment of the processing plants between operations. Food processing is thus a water-intensive operation.
The wastewater of such food production has attributes that are distinct from other industrial activities. In particular, food processing wastewater can be characterized as xe2x80x9cfriendlyxe2x80x9d in that it generally does not contain conventional toxic chemicals such as those listed under the Environmental Protection Agency""s (EPA) Toxic Release Inventory. However, food-processing wastewaters can be subject to bacterial contamination that represents a special issue for wastewater reuse.
Food processing wastewaters are distinguished by their conventionally high Biochemical Oxygen Demand (BOD) concentrations, high levels of dissolved and/or suspended solids, nutrients and minerals. If separated or recovered, many of these constituents have value in secondary markets. Reclaimed materials have value through 1) direct in-plant reuse (e.g., recovery of sugars from fruit canning), 2) sale to external markets (e.g., recovery of pasta starch for animal feed or for compost), and/or 3) use in energy recovery (e.g., through biological or thermochemical gasification).
The characteristics and generation rates of food processing wastewater are highly variable, depending on the specific types of food processing operations. One important attribute is the general scale of the operations, since the range of food processing extends from small, local operations to large-scale national and international producers. This difference in scale not only is relevant in identifying sources of wastewater, but also in determining appropriate reduction or recycling options. In addition to scale differences, the types of food production processes (e.g., poultry, meat, fish, fruit, vegetable, oils and dairy) vary widely, with associated differences in the specific wastewater contaminants. Even within a given food processing plant, the wastewater discharged from different unit operationsxe2x80x94or from different seasonsxe2x80x94may vary with respect to flow rates and compositions. These characteristics will all affect how readily a new reduction or recycling technology can show a return on investment.
In addition to the variability in internal operating conditions, external constraints on food production wastewater management also vary widely. Wastewater disposal costs, which are a key driver for reduction/recycling technologies, will vary based on a given food processor""s location and pertinent regulatory requirements.
With the many obstacles facing wastewater reuse, water traditionally has been used on a once through basis in the food processing industry. However, due to rising utility costs, scarcity of available fresh water, costly more stringent wastewater disposal surcharges and pollution regulations, processors must now look at recycling process wastewaters, and specifically chiller overflow waters, to achieve reduced operational costs.
It is customary in the poultry processing industry to ship live birds to a processing plant where they are bled, scalded, defeathered and eviscerated. Since the scalding operations are usually carried out at about 128 degrees Fahrenheit, the eviscerated birds must be subsequently chilled prior to packaging and shipping. Before the 1960""s, poultry was chilled in layers of ice or immersed in small tanks of ice water. The poultry was chilled using these methods for a sufficient amount of time to reduce the temperature of the poultry to about 40 degrees Fahrenheit or below, after which the tanks were emptied. The use of small, individual single-use tanks required significant resources, including space, employees and water or ice. Because of these disadvantages in single-use tanks, continuous immersion chillers were developed.
Continuous immersion chillers are one or more large tanks where fresh chilled water is continually replenished through which poultry carcasses continuously enter and exit. Modern chillers are equipped with refrigeration units and systems for controlling water volume, direction and agitation. These types of chillers have become more and more efficient, rapid and economical to use.
Presently, the birds are chilled in this continuous fashion in an open tank containing a mixture of ice and water for a period of about 4 to 24 hours. The water chilling step not only is used to cool the birds after scalding, but also is used for the purpose of cleaning away most of the internal and external bacteria of the birds prior to packaging. After the birds have been chilled, they are usually packed in crates with ice and shipped.
The aforementioned procedures suffer from at least three major drawbacks. First, the chiller is quickly contaminated with fecal matter, escherichia coli and salmonellae from the birds. These contaminants are eventually distributed throughout the chiller water and contaminate all of the carcasses moving through the system. Second, the contaminated water of the chiller presents a serious disposal problem. Processors incur substantial toll charges when dumping the contaminated water into either private lagoons or municipal sewer systems. Lastly, continual dumping of the contaminated water necessitates the replenishment with fresh water of the food processing system at significant costs.
In addition to these disadvantages, federal government regulations do not mandate the industry use enough make-up fresh water in the chiller to keep the system clean (only a half gallon per bird), nor does the government regulate how much water should be used in cleanup. Further, many in the industry try to cut costs associated with the water demands by simply using less water, leading to increased incidents of contamination.
In relation to the waste chill water, in recent years there has been increasing awareness and concern with the possibility of poultry and meat being infected with, in particular, pathogenic microorganisms such as species of salmonella or listeria bacteria, with a resultant risk of disease outbreak following human consumption of poultry, meat or meat-based foodstuffs infected in this manner. Throughout the world there are many guidelines and regulations controlling reuse of waste chill water. The poultry industry and the United States Department of Agriculture (USDA) have attempted to deal with these problems by raising the amount of make-up water to an additional half-gallon of fresh water (or four pounds of ice) for each bird that enters the chiller. Although this procedure can maintain the contaminant concentration of the chiller water at a certain level, this amount of new water remains insufficient to keep the system clean, and the process is extremely inefficient because enormous quantities of fresh water are necessary. Moreover, the procedure does not obviate the wastewater disposal problem, but actually enhances wastewater problems.
The industry has further dealt with the problem of pathogenic contamination by constructing chillers with an overflow feature that acts as a skimmer to remove water containing fat particles (floating on top) from the chiller. However, chillers constructed with such overflow features still require enormous amounts of fresh water, and further require a floor drain. Because dirty water flows out onto the floor of the plant, these types of chillers result in unsanitary working conditions.
Treating and recycling some of the wastewater used in poultry processing can save plant managers a great deal of money by cutting both water and sewer costs. USDA recycling regulations now require that the wastewater treatment processes reduce microorganism concentrations by at least 60 percent, including coliformns, escherichia coli, salmonella, and the total microorganism count. The regulations also call for the treated water to have a light transmission (T) of at least 60 percent at 500 nanometers (nm). As the quality of reconditioned water improves, less of the reconditioned water is required to replace a gallon of fresh water in the chiller.
The chemical oxygen demand (COD) and total solids (TS) in wastewater streams from poultry plants usually average 2,000 milligrams per liter (mg/l) each. Waste concentrations vary with the source of the wastewater. They can range from a high of 4,000 mg/l for COD demand and 3,000 mg/l for TS in the giblet chiller effluent, to a low of 250 mg/l for each of these parameters in the wastewater from the whole bird washer. In regard to these USDA regulations, if a poultry plant processes 240,000 broilers per day, it uses at least 120,000 gallons of fresh water daily to chill carcasses. Yet, if 80 percent of that water could be reconditioned, 96,000 gallons of water could be saved each day. At a cost of, for example, $1.90 per thousand gallons for water and sewer charges, this plant could save 24,000,000 gallons of water valued at more than $45,000 per year.
Chemical oxygen demand and total solids loads in the effluent could also be reduced by approximately 200,000 pounds per year (assuming an initial average of 1,000 mg/l of COD and TS, respectively, in the untreated chiller water). If the surcharge on excess COD is 20 cents per pound, the surcharge savings could be upwards of $40,000 per year. Thus the potential savings for water, sewer, and surcharges could total $85,000 per year. Other savings might be realized through by-product recovery and reductions in energy costs.
Accordingly, significant savings can be attained by both recycling some or all of the various wastewater streams and reducing the amount of fresh water usage. Additional savings are also derived through reduction in sewage volume, waste disposal surcharges and total refrigeration load.
The food processing industry in general, and the poultry industry in particular, seeks cost-effective reduction and recycling technologies for food processing wastewaters. These technologies include both source reduction options (technologies to reduce the amount of water used) and treatment options (technologies to reduce the amount or contamination level of wastewaters requiring discharge). Historically, food processors located within or adjacent to municipalities have relied on local publicly owned treatment works (POTW) for wastewater treatment and disposal. Increasingly, this option is becoming less available. Municipal and regional sewer authorities are applying more pressure on industries to reduce their organic (BOD and COD) suspended and dissolved solids loading to the sewers, as in the last five to ten years, there has been an increase in enforcement pressure to comply with wastewater discharge permits and a decrease in federal grants for constructing new and upgrading existing treatment works.
A number of methods are used to reduce wastewater discharge amounts and/or contaminant levels. These methods can be classified into two major classes: source reduction that includes technologies and operations that reduce the amount of wastewater generated in the first place; and treatment options that include technologies and operations that treat wastewater to reduce levels of contamination, either to facilitate in-plant recyclability or to reduce costs of treatment (which are often indexed to contaminant concentrations). Both of these strategies are important to food processing and to wastewater reduction strategies.
The primary requirements of a successful recycling and reuse program are that the treatments be economical, effective, reliable, easily monitored, and avoid the use of chemical additives. Yet no prior reuse program has been able to meet all of these requirements successfully. As one example, dissolved air flotation (DAF) systems combined with disposable filter cartridges have been used to remove the fats, oil and grease combined with the micro-organisms. However, the short life of the disposable type filters (even with attempted air blow-back) and the resultant labor intensiveness of the DAF system preempted success. Ozonation for producing reusable water also has been used in conjunction with DAF systems, but the excessive organic loading required ozone usage well above economical limits. Further, precoat filter systems using such materials as, for example, diatomaceous earth and celite, also proved too labor intensive, too costly, not very reliable, and not readily adaptable for automatic operation. Chemical additives and flocculants to improve filtration also are costly and require complete removal from the final reconditioned water prior to reuse so as not to be considered as a xe2x80x9cFood Additivexe2x80x9d. This drawback of complete removal also applies to residual ozone and filter systems.
Sterilization of wastewater through ozonation alone is being tested as a method to provide sterilization and reduce bacterial counts, permitting closed-loop recycling of rinse and chiller waters. Ozonation works in a manner similar to chlorine disinfection (in both technologies, a reactive gas is introduced to the wastewater stream to chemically disinfect the stream), but avoids the concern of introducing chlorinated organic compounds to the wastewater stream. One disadvantage of ozonation itself is that it leaves ozone in the water stream that will eventually deposit on the food product as a residue.
Further, present testing methods used in connection with the above reuse systems can take from 2 to 3 days to get results on chill water pathogen levels, all the while during this time, contaminated chill water reuse can be ongoing.
Thus it can be seen that there is a need for an effluent purifying system to enable chiller water reuse in the poultry processing industry, which system does not use chemicals or ozone to purify the water. It is to the provision of such purifying systems that the present invention is primarily directed.
Presently, poultry plants in this country are looking for a system that can provide purification and recycling of water used to process poultry. The poultry industry is investigating systems that will enable processors to use the necessary amounts of water to sufficiently clean and process poultry products. Before Jan. 15, 1998, the average poultry plant used approximately 1,300,000 gallons of water per day.
After Jan. 15, 1998, the USDA implemented the xe2x80x9czero tolerance rulexe2x80x9d to prevent fecal matter from entering the chillers used in poultry processing. The rule dictates that no fecal matter is allowed on the birds as they enter the chillers. This rule necessarily caused an increase in the use of water in the poultry industry to try to entirely wash the fecal matter from the bird carcass before chilling.
When the USDA implemented the xe2x80x9czero tolerance rule,xe2x80x9d the average plant water usage jumped to over 2,000,000 gallons of water per day, and in some plants, over 2,500,000 gallons of water per day. This drastic increase in water usage added to the problems the industry was already facing every production day, including the high cost to purchase water, and the shortage of water as a result of the increased demands in other industries. To off-set these problems, many plants turned to wells as a helpful solution to their problems, only to find that in many cases the well water was contaminated by surface water runoff. These plants had no other solutions than to cut back production and in some cases close.
There have been several unsuccessful attempts to recycle process water. In these attempts, companies were perhaps able to filter the water, but they all had at least one major problem. They were forced to rely on chemicals added to the water to meet the USDA guidelines. In such cases, the companies were unable to reduce the pathogens in the water without leaving the residue of the chemical on the product. USDA inspectors and plant employees have had to evacuate a plant testing such attempts in an effort to avoid being overcome with the chemicals that were added to control pathogen levels in their systems.
It would be beneficial to provide a purification system that can filter water to 10 microns, and in some cases as low as 5 microns. In addition, it would be advantageous to reduce the pathogens in the water by up to 99.99%, which would exceed the present USDA requirements of reduction in pathogen levels.
Another problem that faces the industry is the extended delay in receiving pathogen level information back from the testing laboratories. It would be beneficial to provide a system that would allow the industry to have this testing data within seconds, that would otherwise have taken a number of days, and in some cases up to a week to receive with prior reuse systems. Preferably, this system should be able to test the pathogen level at the front of the system, then measures and compares the pathogen levels at the end of the system. This information could then be fed to a PLC and stored where it can be retrieved as needed to verify the affect of the present system. It is provision of such a system that the present invention is directed.
Another advantage over the prior art is a system that incorporates progressive treatment for reconditioning and eventual reuse of water used in the poultry and food industries, especially water used in the chiller. Briefly described, in its preferred form, the present purification system incorporates a plumbing network, an automatic filtration assembly, an ultraviolet disinfection assembly and a water test assembly. The used process water is first filtered to reduce or eliminate the amount of particulate matter in the water. The water can be filtered by one or more stages of filters. The water is then passed through a source of ultraviolet energy to reduce or eliminate the pathogens in the water. The water continuously is monitored for the system""s purification effectiveness. It is particularly adaptable for automatic and continuous operation without addition of and subsequent possible reentry of treatment products and chemicals.
The present invention provides a continuous effluent purifying system that utilizes ultraviolet (UV) energy as one step in the sterilization process. The UV energy destroys nearly all forms of harmful microorganisms and pathogens in the water. Because the wastewater in the process line is sterilized, it can be reused and when necessary and disposed of easily.
Although the present process and apparatus advantageously can be utilized in reconditioning various wastewaters, and particularly those in the poultry and food processing industries, it has been found that the present process is especially useful for reconditioning overflow chill water for direct reuse in conventional submerged poultry liquid chill tanks. Further, the present system can be used to recondition the inside/outside bird wash water, as well as the final bird rinse water. Other food processing industries in which the present invention has application include the pork, beef and diary food processing industries.
Accordingly, it is an object of the invention to provide a system for inexpensively reconditioning wastewater in the poultry and food processing industries.
It is a further object of the present invention to purify chill water from poultry chill water tanks and other poultry processing wastes water for direct reuse in lieu of a continuous, once through fresh water system.
It is another object of the present invention to provide a purification system that passes the waste water through a series of assemblies, including an automatic filtration assembly, an ultraviolet disinfection assembly and a water testing system, wherein treatment chemicals and filtration aiding additives are not used, and wherein the reused waste water conforms to current USDA regulations for acceptable water quality for reuse.
It is yet another object of the invention to provide a wastewater recycling system that exposes the wastewater to UV energy.
These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.